Method of treating rails



Patented Dec. 7, 1937 METHOD OF TREATING RAILS John Brunner,.Chicago, IlL, and Arthur D. Beers, Gary, Ind.; Cora M. Brunner executrix of said John Brunner, deceased No Drawing. Application May 16, 1933' Serial No. 671,422

2 Claims.. (Cl. 148-20) This invention relates to an improvement in the treatment of rails and more particularly to an improved method of cooling rails from a temperatemperature below the critical range and to room temperatures. Y

One of the objects of the present invention is to provide a method of cooling rails which will effect the substantial elimination from the rail interior of deleterious fissures and so-called shatter cracks.

Another object of the present invention is to provide a method of cooling which will further provide for the hardening of the ends of the rail heads.

Still another object of the present invention is to provide an improved rail product..

Other objects and advantages will become apparent as the invention is more fully disclosed.

In accordance with the objects of the present invention we have devised a method of cooling rails which is applicable to the rail at the conclusion oi the. usual rail fabricating process. Railroad rails are usually rolled or mechanically deformed to shape, size and configuration at a so-called hot working temperature which temperature normally lies above the upper critical temperature of the steel comprising the rail. At the conclusion of the rolling operation the temperature of the rail is still above this upper critical temperature and the object of the present invention is to provide a means or method of cooling the rail from this temperature to atmospheric temperatures without permitting the development therein of the so-called fissures or shatter cracks and at the same time obtain a desired or preferred degree of hardening in the headof the rail at and adjacent to its extreme ends.

The present invention contemplates as steps in its cooling method a cooling of the rail at the normal hot bed cooling rate to a temperature approximating but above the upper critical temperature of the steel comprising the rail. The head of the rail adjacent the extreme ends thereof is then quenched through the critical range by the application thereto of a cooling medium. The entire rai1 thereafter is permitted to cool at the normal hot bed cooling rate until the temperature of the rail head intermediate the quenched ends 4 has cooled down to a temperature approximating 350 C. The entire rail is then placed within a heat insulated chamber wherein the rate of cooling can be closely controlled and the rail is permitted to cool at a relatively slow rate throughout the temperature range between 350 C. and

100 C. At the conclusion of this retarded cool ing the rail may be then, cooled at any desired Y rate down to atmospheric temperatures. ture above the critical temperature range to a The application of the above defined method of cooling a rail must be modified in certain details in accordance with the specific composition and car'- bon content of the steel comprising the rail. It is well recognized that the upper critical temperature will vary with respect to variations in the steel composition and with the carbon content of any specific steel cdmposition. It is also recognized that the lower critical temperature or transforming temperature will vary also with respect to the steel composition and the carbon content of any specific steel composition and that it will also vary with respect to the rate at which the steel is cooled from a temperature above the upper critical temperature. Accordingly, with this knowledge at hand one skilled in the art and with the knowledge of the objects of the'present invention can withany given rail steel composition and carbon content adapt the first three steps of the above defined process to obtain the-re- I sult desired by the applicants without further detailed instruction concerning the same.

With respect to step 4 of the above identified method of the present invention we have found that the specific rate of retarded cooling through the temperature range of 350 C. to 100 C. must be varied with respect to the specific steel composition and the carbon content thereof in order to obtain the desired results. ing also must be varied somewhat with respect to the particular cross-sectional area of the rail.

As an illustration of the practice of the present invention, we will describe as a specific embodiment of the same the application of the method to a steel rail having the following approximate composition and carbon content:

Carbon 0.67 to 0.80 Manganese 0.70 to 1.00 Phosphorus maximum 0.04

Silicon 0.10 to 0.23

This rate of cool thereof is quenched by spraying the rail head at these points with a cooling medium preferably compressed air until the temperature of the surface of the ends of the rail head at least approximates 500 C. Thereafter the rail is permitted to cool at the normal hot bed cooling rate until the temperature of the head of the rail intermediate its quenched ends has reached a temperature approximating but not below about 350 C. The rail is then removed from the hot bed and placed in a heat insulated chamber wherein the rate of cooling of the rail between the temperatures of about 350 C. and about 100 C. may be regulated to approximate C.

per hour. This rate of cooling will require a time interval of approximately 10 hours. At the conclusion of this retarded cooling the rail may be then removed if desired and permitted to. cool at any desired rate down to atmospheric tempera tures. It is not necessary that after the rail has cooled to a temperature approximating 100C.

that it be removed from the chamber and if desired it may be left in the chamber until it has cooled to a temperature approximating atmospheric temperatures.

The specific construction of the heat insulated chamber to obtain the retarded cooling is, of

course, immaterial for the purposes of the present invention and may be varied widely without departing essentially from the present invention to meet the particular demands of associated apparatus in the interests of economy of either space or operation.

It is impossible to supply accurate data relative to the variation of the hardening elements in the rail steel as there seem .to be many yet undetermined factors other than the chemical composition that will slightly afiect the, rate of cooling in the range 350 C. to 100 C., and although we know that greater care and a slower rate of cooling has to be applied to steel with higher hardening properties than steel with lower hardening properties, a definite statement as to the effect of the chemical composition on the rate of cooling would be more or less arbitrary and not accurate.

In our experiments we have found that the maximum rate of cooling in the range of 350 C. to 100 C. should not be over 30 0. per hour in order to avoid shatter cracks and we have,-therefore, placed the rate of approximately 25 C. per hour as a safe rate for the regular carbon steel rails. with the use of higher silicon or man-' ,ioi,o4t'

ganese, or the addition of chromium, the rate may have to be further reduced in order to obtain the desired results. The rate of cooling the rails under the normal hot bed method of cooling is about 0. per hour when the rails reach the upper temperature range at which we propose to slow up the rate of cooling.

Having broadly and specifically defined the present invention and described one specific embodiment thereof together with a description of the variable factors inducing or controlling further modificationsand adaptations of the broad method, it is believed apparent that many modifications and adaptations of the cooling method of the present invention can be devisedwithout essentially departing from the present invention and all such modifications and departures are contemplated as may fall within the scope of the following claims.

What we claim is;

1. In the cooling of rails from a temperature above the upper critical temperature to atmospheric temperatures, the method which comprises cooling the rail to a temperature approximating but above the upper critical range, quenching the head of the rail at and adjacent its ends to a temperature below the critical range, cooling the remainder of the rail at the normal hot bed cooling rate until the head of the rail intermediate the quenched ends thereof approximates a temperature of 350 C. and retarding the cooling of the rail between the temperatures of 350 C. to about C. at a rate'determined by the specific steel composition and carbon content thereof.

2. The method of manufacturing rails which comprises hot rolling the rails to the desired size, shape and configuration, cooling the rail at a normal hot bed rate to a temperature approximating but above the upper critical range, quenching the head of the rail at and adjacent its ends to a temperature below the critical range, cooling the remainder of the rail at the normal hot bed cooling rate until the head of the rail intermediate the quenched ends thereof approximates a temperature of 350 C. and retarding the cooling of the rail between the temperatures of 350 C. to about 100 C. at a rate determined by the specific steel composition and carbon content thereof.

JOHN BRUNNER. ARTHUR D. Entries. 

